Numerical simulation of plasma transport in Saturn's inner magnetosphere using the Rice Convection Model

We use the Rice Convection Model to simulate plasma transport in Saturn's inner magnetosphere, 2 < L < 12, where L = equatorial distance in planetary radii. By incorporating a continuously active distributed plasma source derived from neutral cloud modeling, the simulation shows alternating longitudinal sectors (fingers) of inflow and outflow. Their initial development confirms the retarding effects of the Coriolis force and the pickup current. In their further nonlinear development, the inflow fingers become much narrower in longitude than the outflow ones, which may explain a previously unexplained feature of the Cassini Plasma Spectrometer (CAPS) observations. Our analysis confirms that the narrower inflowing fingers have much larger radial speeds than the broader outflowing sectors. We analyze the corotation lag and find that in the innermost region (L < 5) the pickup current is the major driver of the corotation lag, but in the more distant region (L > 5) both the pickup current and the Coriolis acceleration contribute significantly to the corotation lag. We compare our simulation results with observational results from CAPS data. For the radial flow component, the simulation results fit observations reasonably well. In the azimuthal component, there are significant differences in the magnitude and radial structure of the corotation lag, which may provide guidance for future refinement of the plasma source model.